Liquid heating apparatus

ABSTRACT

A liquid heating apparatus has a first mode of operation in which a first volume of water can be heated and a second mode of operation in which a second, smaller volume of water can be heated and automatically dispensed. The first mode may be provided by a removable liquid heating vessel. The second mode may be provided by a second heating chamber comprising a heater arranged to heat liquid and dispense it through an outlet. The second heating chamber is filled with water from the removable liquid heating vessel.

This application is entitled to the benefit of, and incorporates by reference essential subject matter disclosed in PCT Application No. PCT/GB2008/004249 filed on Dec. 23, 2008, which claims priority to Great Britain Application No. 0725235.6 filed Dec. 24, 2007.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates to a liquid heating apparatus for heating/boiling liquids such as water.

2. Background Information

There is a common need almost all over the world to heat water in order to make beverages. In the UK and other parts of Europe, it is common for most households to own a kettle which is used to boil water for making occasional beverages. In larger establishments and also in other parts of the world, it is more common to keep a body of water hot or boiling for a prolonged period of time—possibly all day—in order to be able to make such beverages “on demand”, i.e. without having to wait for the water to heat up from room temperature. An example of this would be a traditional electric urn or, more commonly in Asia, a so-called airpot.

Both of these arrangements have their disadvantages. In the case of the kettle, the time taken for the water to heat from cold (i.e. the temperature from which it is drawn from the tap) is seen as inconvenient to users, even those using very high power kettles (of the order of 3 kilowatts). This is particularly so given the difficulty in estimating the volume of water required when the kettle is being filled and the attendant tendency to boil more water than is needed which of course increases the time taken for it to boil. On the other hand, if water is kept for a prolonged period of time either at or just below boiling, a significant amount of energy will be required to counter the unavoidable heat loss.

Recently, devices attempting to bridge this gap have been commercialized. These are said to be able to deliver a cupful of hot water from a reservoir of cold water within a matter of seconds. However, these devices are typically based on a tubular flow heater and the applicant has appreciated some significant drawbacks to this arrangement. Firstly, as is typical of tubular flow heaters, heating must be ceased before the water in the tube reaches boiling point in order to avoid the danger of the heater overheating through hot spots created by pockets of water vapor and/or the pressure inside the tube building up too high. Another drawback is that although the heater heats up relatively quickly, there is inevitably an initial volume of water which passes through the heater which is not heated to the target temperature. This mixes with the water produced later, itself still not at boiling point, to reduce the average temperature of the water. The combination of these two factors means that in practice the water provided by such devices is at well below boiling point by the time it is dispensed, making it unsuitable for example for making tea and thereby limiting its consumer appeal.

The Applicant has further appreciated that most users will still need to keep a conventional kettle in addition to a one-cup hot water dispenser of the type discussed above, for when a larger quantity of truly boiling water is needed. This creates problems in terms of space taken up in the kitchen.

SUMMARY OF THE DISCLOSURE

When viewed from a first aspect the present invention provides a liquid heating apparatus having a first mode of operation in which a first volume of water can be heated and a second mode of operation in which a second, smaller volume of water can be heated and automatically dispensed.

It will be seen by those skilled in the art that in accordance with the invention a single apparatus can be used either to heat and dispense a small volume of water rapidly, or to heat or boil a larger quantity of water more conventionally. This has the advantage of allowing the user to select the appropriate mode of operation according to the volume of water required at any particular time, but without the cost associated with separate appliances for these tasks or the need to find space for multiple appliances on a kitchen worktop. Of course it should be understood that the relative volumes of water that can be heated in either mode is determined by the relative maximum capacities; at least in preferred embodiments the first mode of operation could be used to heat a volume of water that is sufficiently small that it could have been heated in the second mode instead. The volume of water that can be heated in the second mode may be fixed or might be variable—e.g. by a user.

The apparatus could be provided with separate reservoirs for the two respective modes of operation, but in preferred embodiments a common reservoir is provided. This could be arranged to dispense water (or another liquid) to respective heating arrangements depending upon whether the first or second mode of operation was being employed, but in preferred embodiments the apparatus is arranged to heat all the water in the reservoir in the first mode of operation, or a smaller, predetermined amount of water from the reservoir in the second mode of operation.

The apparatus preferably comprises a removable reservoir which is advantageous in facilitating filling, since the reservoir can be removed from the rest of the apparatus and taken e.g. to a tap to fill it. In particularly convenient embodiments, the apparatus is also arranged such that water heated in the first mode of operation can be manually dispensed from the removable vessel. The removable vessel can, preferably, resemble an ordinary kettle and it will be appreciated therefore that in these embodiments the apparatus essentially comprises a standard water boiling kettle but the apparatus is also configured to be able to heat and dispense water “on demand” if the volume required is small enough.

A common heating means could be employed to heat water in either the first or second mode of operation. For example, a reservoir could comprise means to divide off a small volume therefrom which can be heated in the second mode of operation. In other embodiments, independent heating means are provided for the first and second mode of operation respectively. This might have some advantages in terms of optimizing each heater for its particular use and also lends itself particularly to embodiments where essentially a complete water boiling kettle is provided for operation in the first mode but which, when placed on the apparatus, allows water from the kettle to enter the heater for the second mode of operation. It will be appreciated that in such embodiments the kettle could be operated independently of the rest of the apparatus, only needing to be placed on the rest of the apparatus when the second mode of operation was required.

Such arrangements are novel and advantageous in their own right and thus when viewed from a further aspect the invention provides an apparatus for heating liquid comprising a removable liquid heating vessel comprising a heater for heating liquid therein, the apparatus further comprising a second heating chamber arranged to heat liquid and dispense it through an outlet, wherein said second heating chamber is filled with liquid from the removable liquid heating vessel.

Preferably one or both heaters are arranged to heat water to boiling. In comparison with the first aspect of the invention the removable liquid heating vessel provides the first mode of operation and the second heating chamber provides the second mode.

In accordance with all the aforementioned embodiments, it is preferred for the heater for heating liquid in the first mode of operation, e.g. the heater of the liquid heating vessel in the aspect of the invention set out above, to comprise a heater plate with a resistance heating element, e.g. a sheathed element, formed on or mounted to the underside of the plate. Preferably the heater is arranged to close an opening in the base of the vessel as is well-known in the art of kettles.

Where an independent heater for the second mode of operation is provided, e.g. the heater of the second heating chamber in the aspect of the invention set out above, this could take any convenient form, e.g. a tubular heater or some other form of flow heater, but preferably a chamber is provided in which the liquid is heated to the desired temperature and then dispensed.

The automatic dispensing in the second mode of operation could be effected by any suitable means. For example, a pump could be employed or the apparatus might be arranged such that the liquid is heated in an upper part thereof and dispensed lower down through hydrostatic pressure. In preferred embodiments, however, the water is arranged to be boiled in the second mode of operation and is dispensed from the apparatus with the aid of steam pressure generated during boiling.

In some embodiments of the invention a common mechanism is provided to cease heating of the liquid when it has reached a predetermined temperature, regardless of whether this is in the first or the second mode of operation. This could take any convenient form, e.g. electronic, and may be dependent upon the temperature to which the liquid is being heated. In preferred embodiments in which water is boiled in both modes of operation, the common means preferably comprises a steam switch, e.g. one comprising a snap acting bimetallic actuator, as is well-known in the art.

In other embodiments independent means are provided to cease heating in the respective modes. For example where a removable liquid heating vessel is provided, a conventional steam switch could be provided. This for example allows such a removable vessel to be as close as possible to a standard kettle which is beneficial both in terms of user acceptance and in being able to minimize re-tooling.

The removable liquid heating vessel preferably comprises valve means for selectively allowing liquid into the second heating chamber when the vessel is installed on the appliance and preventing leaking when it is removed. The valve means could be provided in the vessel body, but preferably it is provided in a heater plate closing an opening in the base of the vessel. This is beneficial in having the valve lowermost in the vessel but also means that a standard heater plate incorporating the valve can be produced, thereby allowing appliance manufacturers to use appliance bodies that have already been tooled.

Although not essential, preferably valve means are also provided on the second heating chamber. Preferably such valve means are configured to close when there is a predetermined amount of water in the second heating chamber. This allows the second heating chamber to fill automatically to the required level. It could for example comprise a float valve. In accordance with one set of embodiments, a freely floating valve member is employed, which is more robust than a flap valve. Advantageously, such a valve member is received in a housing which permits liquid flow through it but retains the valve member, the valve member having an upper position in which it is against a valve seat to close the valve and a lower position where it is retained in the lower part of the housing. The valve member might take any convenient form. For example it could comprise a ball. Alternatively it could be pill, discus or squat-cylindrical in shape. In a preferred set of embodiments the valve member is downwardly tapering, e.g. frusto-conical. This has been found to minimize the chance of the valve member sticking during use.

Preferably the second heating chamber valve means is configured such that increasing pressure in the heating chamber tends to increase the closure pressure on the valve arising from the buoyancy of the valve member. Preferably it comprises a resilient collar against which the valve member is pressed by internal pressure in the second heating chamber. This helps to prevent leakage of water or steam when the removable vessel is removed.

Where, as is preferred, separate heaters are provided for the two respective modes of operation, preferably the apparatus comprises a switching arrangement which only permits energization of one of said elements at time. This is advantageous as it allows each heater to be high power without running the risk of overloading the mains electrical supply by both being energized at once. In a simple exemplary embodiment the switching arrangement could comprise a change-over switch such as a rocker switch. Where provided the steam switch preferably acts on the aforementioned switching arrangement to switch off whichever heater is being energized.

The above-mentioned arrangement is considered to be novel and inventive in its own right and thus when viewed from another aspect the invention provides a switching arrangement for an electrical appliance, said switching arrangement comprising a switch having a first position in which a first circuit can be powered, a second position in which a second circuit can be powered and a third position in which neither of said circuits is powered, said arrangement further comprising a thermally responsive actuator arranged to act on said switch so as to move the switch from either of said first or second positions to said third position upon said actuator reaching a predetermined temperature.

In other embodiments an electronic or electro-mechanical arrangement is employed to prevent simultaneous energization. For example in one set of embodiments a relay is employed in series with the electrical supply to one of the heaters and is arranged such that the contacts thereof are opened when power is supplied to the other heater. Of course the skilled person will readily conceive of equivalent means for achieving the same function electronically. Preferably the arrangement is such as to cut off power to the removable liquid heating vessel when the heater of the second heating chamber is energized. This is beneficial in that it allows the electrical arrangement in the liquid heating vessel to be entirely standard. For example the relay or other switching arrangement could simply cut power to a cordless connector such as the Applicant's P72 connector which is used to supply power to the liquid heating vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 is a schematic diagram showing the main parts of an apparatus embodying the invention;

FIG. 2 is a schematic circuit diagram illustrating the electrical switch arrangement for the two heaters;

FIGS. 3 a to 3 d are a series of schematic diagrams showing use of an embodiment of the invention;

FIG. 4 is a further schematic diagram of a second embodiment;

FIG. 5 is a perspective view of a third embodiment of the invention;

FIG. 6 is a perspective view, from a different angle, of the embodiment of FIG. 5 with the jug kettle part removed;

FIG. 7 is a view similar to FIG. 6 with the outer cover removed;

FIG. 8 is a partly exploded view of the parts above the heating chamber;

FIG. 9 is cross-sectional view through the heating chamber;

FIG. 10 is a different section through the heating chamber;

FIG. 11 is an enlarged sectional view of the valve between the jug kettle and the heating chamber;

FIG. 12 is a perspective view of the lower part of the dispensing chamber;

FIG. 13 is a sectional view through the dispensing chamber; and

FIG. 14 is schematic circuit diagram for the appliance.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows the basic parts of an apparatus embodying the invention. In this embodiment there is an almost-standard jug kettle 2 having a lifting handle 4 and a pouring spout 6. The kettle is fitted with a heater arranged to close an opening in the base thereof and comprises a sheathed heating element mounted to the underside of a metal plate. The kettle 2 also comprises the Applicant's standard U17 control unit in order to switch off the heater in the event that it overheats due to being switched on dry or boiling dry. As is well known in the art such a control unit includes the male part of a 360 degree cordless electrical connector. The female part of the connector 8 is visible on the base part of the apparatus 10.

Where the kettle 2 differs from an ordinary one is that on its base it comprises a self-closing valve (not visible) which can be opened by penetration of a tube 12 protruding from the base 10 when the kettle 2 is placed on the base 10. At the lower end of the tube 12 is another valve in the form of a float valve 13, controlling the entry of water from the kettle 2 to a heating chamber in the base 10.

The heating chamber inside the base of the apparatus 10 has another heater 30 at the underside thereof which is similar to the heater in the kettle 2. As well as the inlet controlled by the float valve 13 as just described, the base heating chamber is connected to a dispensing spout 14 which protrudes from the base part 10 and ends with a downward loop for dispensing heated water into a cup 16 or other receptacle placed beneath it.

Also communicating with the heating chamber and rising from the base 10 of the apparatus is a vertical steam tube 18 with a narrow neck at its upper end, beyond which is a thermally responsive snap-acting bimetallic actuator 20. Although not shown in the schematic representation of FIG. 1, the bimetal 20 is positioned such that it also lies above the spout 6 of the kettle 2 when it is positioned on the base unit 10.

FIG. 2 is a schematic circuit diagram showing the switching arrangement. It will be noted from this that the bimetal 20 acts on a change-over type rocker switch 36. The rocker switch 36 has three positions. In the left and right positions it can complete a circuit between a common terminal 22, connected to the live side of the mains supply, and either one of two other terminals 24, 26, connected respectively to the element 28 in the kettle 2 and the element 30 in the base heating chamber. In the central position of the switch 36, neither circuit is completed.

This arrangement allows either element 28, 30 to be energized or neither to be energized, but does not physically allow both elements to be energized at the same time. Consequently each element can be at the maximum power rating for the mains supply—e.g. 3 kW in the UK. The bimetallic actuator 20, when it reaches its operating temperature (e.g. ninety degrees C.), after coming into contact with steam, acts on the switch 36 to return it to the central, open position (depicted in FIG. 2) in which neither element is energized.

In series with the kettle element 28 are the respective live and neutral pole switch contact sets 32 of the U17 control unit. In series with the base heating chamber element 30 are a simple bimetallic thermostatic switch and a thermal fuse switch or two bimetallic switches (not shown). These respective further switches ensure that the elements are de-energized in the event of overheating—e.g. due to being switched on dry or boiling dry.

Operation of the apparatus will now be described with additional reference to FIGS. 3 a to 3 d. FIG. 4 a shows the apparatus with the kettle 2 placed on the base part 10 and with a cup 16 placed beneath the dispensing spout (not visible). In use the user removes the kettle 2 from the base unit 10 and fills it from a tap in the conventional way (FIG. 4 b). It is then replaced on the base part 10, thereby allowing the tube 12 to penetrate the bottom of the kettle and to allow water to be drawn out from it subject to the float valve 13 being open (i.e. if the base heating chamber is empty).

In a first mode of operation a user can boil a relatively large volume of water (e.g. up to two liters). This is done by selecting the appropriate position for the rocker switch 36. This energizes the kettle element 28 so that it boils the whole contents of the kettle 2. When the water has boiled, the steam produced will cause the bimetal 20 to operate which in returns the rocker switch 36 to the central, off position which interrupts power to the cordless connector 8 and so de-energizes the element 28 in the kettle. Of course, instead of this arrangement a more conventional steam switch arrangement could be employed in the kettle 2 itself. With a 3 kW heating element it would take approximately 4 minutes to boil two liters of water. Once the element has been switched off after the water has boiled, the kettle 2 can be picked up and the water poured out in the normal way (FIG. 3 c).

If instead the user requires only a cupful of boiling water, a second mode of operation can be employed. This is done by selecting the other position of the rocker switch 36 (FIG. 3 d) and thereby energizing the in the base chamber heater 30.

This rapidly heats the small volume of water in the chamber to boiling, with the steam thereby produced entering the steam tube 18 and actuating the bimetal 20 and returning the switch 36 to the central position so switching off the element. The increase in pressure associated with the water in the chamber being boiled forces it up through the dispensing spout 14 and into the cup 16. A cupful of water can be boiled and dispensed in approximately 30 seconds.

FIG. 4 shows schematically a further embodiment. This has a similar arrangement of a removable kettle 2′ with its own element (not shown) and a side-entry water feed tube 12′ for drawing water from the kettle 2′ for rapidly heating and automatically dispensing a small, predetermined body of water through the spout 14′ to the cup 16. In this embodiment however, instead of a heater on the underside of an enclosed base heating chamber, there is a flow heater 30′ for heating the water for the second mode of operation.

Thus it will be appreciated by those skilled in the art that the embodiment described above allows a user the flexibility to be able to boil a cupful of water very rapidly, or to boil a kettle full of water in the usual way, but without having to buy, and find storage space for, two separate appliances.

The embodiment described is merely one example of how the invention can be implemented. Many variations and modifications can be made. For example rather than having two separate heating elements for the two modes of operation, a single common element could be provided.

FIG. 5 shows a perspective view of a further embodiment of the invention. This broadly comprises a removable liquid heating vessel in the form of a jug kettle 40 which is placed on a stand 42 which also serves to support a hot water dispensing chamber 44 with its dispensing spout 45 by means of a pillar 46. The kettle 40 is shown with the lid and outer handle molding removed. This reveals a standard steam switch 48 such as the applicant's R48 steam control which is used to switch the kettle off when water inside it boils.

FIG. 6 shows the apparatus with the kettle removed. This reveals a 360° cordless electrical connector 50 such as the applicant's P72 connector located centrally within the region of the base 42 which receives the kettle. To one side of the cordless electrical connector 50 is the outer housing of water valve 52, the purpose of which will be described later.

Also more easily visible in this drawing is the on/off switch 54 on top of the hot water dispensing chamber 44 and the drip tray 56 which is directly beneath the spout 45 (not shown in FIG. 6).

FIG. 7 shows a view of the main parts of the appliance with the outer covers removed. Thus in the lower part of the appliance there can now be seen a heating chamber 58 with which the valve 52 selectively communicates. Extending from the side of the heating chamber 58 are two tubes 60, 62 which connect the interior of the heating chamber 58 to the interior of the dispensing chamber 44. The purpose of these two tubes will be described later.

FIG. 8 shows a partially exploded view of the parts above the heating chamber. This shows that the 360° cordless connector 50 is received in a special recess 60 in the top face of the heating chamber 58. A channel 62 is provided to accommodate the wires coming from the connector 50. The connector 50 is held in place by a plate 64 which is screwed, riveted or otherwise attached to the top of the heating chamber 58. The securing plate 64 also provides the outer valve housing 52. The outer valve 52 housing fits over an upstanding annular wall 66 on the top of the heating chamber with a novel resilient annular sealing member 68, which will be described in more detail later, interposed between them.

The heating chamber 58 is formed from upper and lower parts which are clamped together by clamp rings 70, 72 which are screwed together by a series of boss and screw arrangements 74.

FIG. 9 shows a vertical cross-section through the heating chamber 58. From this figure can be seen the sheathed resistance heating element 76 bonded to an aluminum diffuser plate 78 which is in turn bonded to the underside of a stainless steel heater plate 80, the foregoing construction being similar to that conventionally used in water-boiling kettles. The heater plate 80 is attached to the upper body of the heating chamber 58 by means of a peripheral channel 82 which is crimped over a downwardly depending wall portion of the heating chamber in accordance with the applicant's Sure Seal system which is described in greater detail in WO 96/18331.

Also visible in this figure is a section through one of the tubes 60 connecting the heating chamber 58 to the dispensing chamber (not shown). This is the outlet tube for conveying boiling water from the heating chamber 58 to the dispensing chamber. It will be apparent from the Figure that inside the chamber the outlet tube 60 extends in a right angle arrangement to terminate in a downwardly depending tube portion 84, the end of which is a few millimeters above the heater plate 80.

FIG. 10 also shows a vertical cross-section through the heating chamber 58, although in this instance the section is taken through a plane parallel to that of FIG. 9. This shows the other tube 62 connecting the heating chamber 58 to the dispensing chamber which is a vent tube. The lower end of the vent tube 62 fits over a spigot 86 which opens into a hole at the top of the interior of the heating chamber 58.

FIG. 11 shows a vertical cross-section through the kettle 40 seated on top of the heating chamber 58. In this figure, the view has been enlarged to show the valve arrangement more clearly and some components have been omitted to enhance clarity further. The kettle 40 has a side wall 88. The underside of the kettle is closed by a circular stainless steel heating plate 90, on the underside of which is provided an aluminum diffuser plate 92 and a sheathed resistance heating element (not visible).

A hole is formed towards the edge of the heater plate 90 to accommodate the vertically protruding spigot portion 94 of the kettle part of the valve mechanism. This spigot portion 94 is sealed against the hole in the heater plate 90 by means of a grommet 96. Beneath the spigot portion 94, the kettle valve part comprises two concentric annular shrouds: an inner shroud 98 and an outer shroud 100. The diameter of the outer shroud 100 is such that it fits over the outer housing 52 of the heating chamber valve part and it has a beveled edge to aid location.

Between the spigot 94 and the inner shroud 98 is a sprung valve arrangement comprising a vertically movable valve member 102 which has at the top a valve head 104 which is biased towards a corresponding valve seat 106 by a compression coil spring 108. The coil spring acts between the underside of the valve seat 106 and a ring 110 at the bottom of the valve member 102. In the configuration shown in FIG. 11, an upward force is being applied to the lower ring 110 of the valve member thus lifting the valve head 104 away from the valve seat 106 to permit water to pass through the valve. Equally, however, it will be seen that when this force is removed, the coil spring 108 acts to close the valve and therefore prevent further passage of water.

The components provided on the heating chamber side of the valve arrangement comprise the outer housing 52 (mentioned previously with reference to FIGS. 6, 7 and 8) having a central, chamfered opening which receives the inner shroud 98 of the kettle valve housing. This outer housing 52 therefore passes, during coupling of the two valve parts, between the inner and outer shrouds 98, 100 of the upper part. Inside the outer housing 52 is the annular sealing member 68 which provides a fluid-tight seal against the upwardly projecting annular wall 66 which is an integral part of the top of the heating chamber 58. The sealing member 68 has a central annular protrusion which forms an upwardly open annular channel which receives and seals against the lower edge of the inner shroud 98 of the kettle valve part.

On the lower face of the sealing member 66 is an angled annular flange 112 which extends radially outwardly so that it has a degree of flexibility in the axial direction.

Beneath the sealing member 66 is a generally frusto-conical float valve member 114 which is able to move vertically but which is constrained in its downward travel by a valve stop member 116. The top surface of the float valve member 114 presses against the angled annular flange 112 when it is in the upper portion of its travel.

FIG. 12 shows a perspective view from above of the dispensing chamber 44 with the upper cover removed. FIG. 13 shows a vertical cross-section through part of the chamber with the upper cover in place. The main part of the dispensing chamber 44 a is broadly bowl-shaped with the dispensing spout 45 in a distinct recess 44 c at the center. Extending around part of the rear edge is a raised, generally horizontal platform portion 44 b into which the outlet pipe 60 and vent pipe 62 from the heating chamber emerge. It will be noted that these two tubes 60, 62 extend vertically some way into the dispensing chamber.

Mounted outside the dispensing chamber (but shown in FIG. 12 for reference) is an R48 steam switch 188 to which is attached the on/off rocker switch 54. A vertical chimney 120 extends through, but is isolated from, the dispensing chamber 44 and opens just beneath the bimetallic actuator (not clearly visible in FIGS. 12 and 13) of the steam switch 118. This allows cool air to pass over the bimetallic actuator after it has operated in order to allow it to reset relatively quickly.

As may be seen most clearly from FIG. 13, the tube forming the outlet spout 45 extends vertically some way into the dispensing chamber 44 inside a concentric downwardly open tube 122 of slightly larger diameter which is mounted to the upper cover of the dispensing chamber. The downwardly open tube 122 extends down just short of the annular recess 44 c in the center of the main part of the dispensing chamber 44 a.

FIG. 14 shows a schematic circuit diagram showing the main electrical connections between various parts of the appliance. To the left of the diagram may be seen the line, neutral and earth connections from the mains lead (not shown). The switch contacts of the steam switch 118 provided in the dispensing chamber are connected electrically in series between the line pole and the coil of a relay 124 (although not shown in this schematic diagram, some form of rectification might be provided). The contacts of the relay 126 are of the change-over type with the common contact 126 a connected to the line pole. The normally-off relay contact 126 b is connected to the heating element 76 provided on the base of the heating chamber 58. Although not shown in the Figures, the electrical connection to this element 76 is made by means of a modified U-series control having its characteristic pair of overheat-protection bimetallic actuators which act on respective normally-closed contacts 128 a, 128 b on the line and neutral side respectively of the element. An indicator neon 130 is connected, in series with a suitable resistor 132, across the element 76 to indicate when the element is energized.

The normally-closed relay contact 126 c is connected to the central, line terminal of the cordless electrical connector 50. The neutral and earth terminals are connected directly to the corresponding inputs from the mains lead.

To the right of the diagram in FIG. 14 is depicted the conventional electrical arrangement found in a kettle. Thus, the heating element 134 is connected in series with the normally-open contact of the steam switch 48 and also in series with the normally-closed contacts 136 a, 136 b which are acted on by the overheat bimetals of a U17 control. Again, an indicator neon 138 and corresponding resistor 140 are connected across the element 134 to indicate when it is energized.

Operation of the embodiment described above with reference to FIGS. 5 to 14 will now be described.

As with the previous embodiments, the appliance of this embodiment can be operated in two separate modes. In the first mode, the kettle 40 can be removed, filled and then replaced on the base. To start boiling, the on switch (not shown) is pressed to close the contacts of the steam switch 48. In the normal state shown in FIG. 14, power can then be supplied through the cordless connector 50 to energize the element 134. Unless the user switches off again, heating will continue until the water in the kettle boils which causes the steam switch 48 to operate and disconnect the power to the element. The kettle 40 can then be lifted up again and the boiling water poured out of its spout in a conventional manner.

However, if a user wishes to boil and dispense just a cupful of water, he or she can operate the appliance in a second mode of operation which will be described below.

When the appliance is first used, or the heating chamber 58 has otherwise been allowed to become empty, it must be filled with water. This is done by filling kettle 40 with water and replacing it on the stand 42. This allows the water in the kettle 40 to drain through the valve arrangement shown in FIG. 11 into the heating chamber. More particularly, as the kettle 40 is replaced on the stand, the lower end ring 110 of the valve member 102 in the kettle valve part is forced up against the force of the coil spring 108 by its contact with the inner annular projection of the sealing member 68. This allows water to flow from the inside of the kettle 40, through the valve spigot portion 94, past the valve member 102 and into the heating chamber 58 through the center of the sealing member 68 and over the edges of the float valve member 114. The vent tube 62 allows air to be displaced from the chamber even after the lower part 86 of the outlet tube has been covered.

As the level of water in the heating chamber 58 rises, the float valve member 114 will gradually be raised by the water until such time as it seals against the annular flange 112 on the lower face of the sealing member 68 with sufficient force to prevent any further water entering the heating chamber 58. If the kettle 40 should now be lifted up again, the coil spring 108 will close the valve head 104 against the valve seat 106 inside the kettle valve housing, thus preventing leakage of water from the kettle. Similarly, the buoyancy pressure of the float valve member 114 against the compliant annular flange 112 at the bottom of the sealing member 68 will prevent water from spurting out of the lower part of the valve arrangement. When the kettle 40 is replaced, although the kettle side of the valve 104, 106 will be opened again, no further water will flow since the float valve member 114 will remain pressed against the annular flange 112.

In order to operate the appliance in the second mode, the user must switch on the switch 54 provided at the top of the dispensing chamber. As will be appreciated by considering the circuit diagram of FIG. 14, this energizes the relay coil 124 to disconnect relay contacts 126 a and 126 c and connect contacts 126 a and 126 b. This has two consequences. The first is that the kettle 40 cannot be operated since power is no longer being supplied to the cordless connector 50, thereby ensuring that the two elements 76, 134 cannot be energized at the same time which would drain an excessive current for an ordinary domestic mains socket. The other consequence is that the element 76 on the underside of the heating chamber 58 is energized and begins to heat the water in the heating chamber.

During the initial stages of heating, the build-up of pressure inside the heating chamber 58 is limited by the vent tube 62 connected to the dispensing chamber 44 which is essentially at atmospheric pressure. This prevents water which has not been sufficiently heated from being ejected via the outlet tube 60 prematurely. It also reduces any tendency of the float valve member to 114 to ‘wobble’ against the sealing member 68. Together with the compliant annular flange 122 this helps prevent further cold water entering the heating chamber during heating.

As the temperature of the water in the heating chamber 58 approaches boiling, the pressure builds up and begins to force water up the outlet tube 60 and so into the dispensing chamber 44. As this continues, almost all of the boiling water in the heating chamber 58 is forced up the outlet tube 60 to fill the dispensing chamber 44. Water will continue to be forced up the outlet tube until the water level in the chamber 58 falls below the lower end of the downward extension of the outlet tube 88.

Turning to FIGS. 12 and 13, it will be seen that boiling water initially enters the side chamber 44 b and thereafter drains into the main part of the chamber 44 a towards the annular recess 44 c in the center and so starts to fill the chamber main part 44 a. As water continues to enter the dispensing chamber 44, the level between the downwardly open tube 122 and the upwardly extending outlet spout 45 rises until the water begins to flow over the top edge of the outlet tube 45 and so down through the spout into a user's cup. This sets up a siphon which causes virtually all of the water in the dispensing chamber 44 to be dispensed through the spout 45.

Once all the water has been forced up from the heating chamber 58 via the outlet tube 60, steam from the heating chamber 58 will be ejected from the top of the outlet tube 60 (as well as form the vent tube 62) and into the dispensing chamber 44. This causes the steam switch 118 to switch off, thereby interrupting power to the relay coil 124 and so disconnecting the heating chamber element 76.

When pressure in the heating chamber has subsided, the float valve member 114 drops down against its stop 16 which automatically refills the heating chamber 58 with water from the kettle 40, assuming it is there and has sufficient water in it. If the kettle 40 is not there, the heating chamber 58 will be refilled next time it is replaced. The kettle 40 therefore acts as a convenient removable reservoir for the heating chamber. This allows a user to produce cups of boiling water repeatedly throughout the day without having to refill the kettle each time, without re-boiling the same water several times (which is often considered to harm its taste by removing dissolved oxygen) and, importantly, without wasting energy by boiling more water than is necessary.

If the heating chamber 58 is operated without any water in it, for example if there is no water in the kettle 40 to refill the chamber after a previous use, then one or other of the bimetals in the modified U-series control protecting the element 76 will operate to open the respective contacts 128 a, 128 b.

Thus it will be seen that a highly versatile appliance is provided which can either be used as an ordinary kettle to heat a relatively large quantity of water or, if only a single cupful of water is required, it can be heated and dispensed very quickly and efficiently by means of the second mode of operation. The kettle 40 then acts as a removable reservoir in this mode of operation which is in itself convenient as it allows easy refilling. The provision of a relay to switch between the two elements avoids an electrical overload.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed herein as the best mode contemplated for carrying out this invention. 

What is claimed is:
 1. A liquid heating apparatus having a first mode of operation in which a first volume of water can be heated and a second mode of operation in which a second, smaller volume of water can be heated and automatically dispensed.
 2. Apparatus as claimed in claim 1 comprising a common reservoir for the two modes of operation.
 3. Apparatus as claimed in claim 2 arranged to heat all the water in the reservoir in the first mode of operation, or a smaller, predetermined amount of water from the reservoir in the second mode of operation.
 4. Apparatus as claimed in claim 1 comprising a removable reservoir.
 5. Apparatus as claimed in claim 4 arranged such that water heated in the first mode of operation can be manually dispensed from the removable reservoir.
 6. Apparatus as claimed in claim 1 comprising independent heaters for the first and second mode of operation respectively.
 7. Apparatus as claimed in claim 6 wherein one or both heaters are arranged to heat water to boiling.
 8. Apparatus as claimed in claim 6 wherein said heater for the first mode of operation comprises a heater plate with a resistance heating element formed on or mounted to the underside of the plate.
 9. Apparatus as claimed in claim 1 in which water is arranged to be boiled in the second mode of operation and dispensed from the apparatus with the aid of steam pressure generated during boiling.
 10. Apparatus as claimed in claim 1 comprising a chamber in which the liquid is heated to the desired temperature and then dispensed for the second mode of operation.
 11. Apparatus as claimed in claim 1 comprising independent control arrangements to cease heating in the first and second modes respectively.
 12. An apparatus for heating liquid comprising a removable liquid heating vessel for heating liquid therein, the apparatus further comprising a second heating chamber comprising a heater arranged to heat liquid and dispense it through an outlet, wherein said second heating chamber is filled with liquid from the removable liquid heating vessel.
 13. Apparatus as claimed in claim 12 wherein said heater of the removable liquid heating vessel is arranged to close an opening in the base of the vessel.
 14. Apparatus as claimed in claim 12 wherein the removable liquid heating vessel comprises valve arrangement for selectively allowing liquid into the second heating chamber when the removable vessel is not removed and preventing leaking when it is removed.
 15. Apparatus as claimed in claim 14 wherein said heater of the removable liquid heating vessel is arranged to close an opening in the base of the vessel and wherein the valve means is provided in the heater closing an opening in the base of the vessel.
 16. Apparatus as claimed in claim 12 comprising a valve arrangement on the second heating chamber.
 17. Apparatus as claimed in claim 16 wherein said valve arrangement is configured to close when there is a predetermined amount of water in the second heating chamber.
 18. Apparatus as claimed in claim 16 comprising a float valve member.
 19. Apparatus as claimed in claim 18 wherein the second heating chamber valve arrangement comprises a resilient collar against which the valve member is pressed by internal pressure in the second heating chamber.
 20. Apparatus as claimed in claim 19 in which water is arranged to be boiled in the second heating chamber and dispensed from the apparatus with the aid of steam pressure generated during boiling.
 21. Apparatus as claimed in claim 12 comprising independent control arrangements to cease heating in the removable vessel and second heating chamber respectively.
 22. Apparatus as claimed in any of claim 21 comprising independent heaters for the removable vessel and second heating chamber respectively.
 23. Apparatus as claimed in claim 22 wherein one or both heaters are arranged to heat water to boiling.
 24. Apparatus as claimed in claim 22 comprising a switching arrangement which only permits energization of one of said heaters at a time.
 25. Apparatus as claimed in claim 24 comprising a relay in series with the electrical supply to one of the heaters and arranged such that the contacts thereof are opened when power is supplied to the other heater.
 26. Apparatus as claimed in claim 24 wherein the arrangement is such as to cut off power to the removable liquid heating vessel when the heater of the second heating chamber is energized.
 27. Apparatus as claimed in claim 1 in which water is arranged to be boiled in the second heating chamber and dispensed from the apparatus with the aid of steam pressure generated during boiling.
 28. Apparatus as claimed in claim 1 comprising independent control arrangements to cease heating in the removable vessel and second heating chamber respectively.
 29. Apparatus as claimed in claim 28 comprising independent heaters for the removable vessel and second heating chamber respectively.
 30. Apparatus as claimed in claim 29 wherein one or both heaters are arranged to heat water to boiling.
 31. Apparatus as claimed in claim 6 comprising a switching arrangement which only permits energization of one of said heaters at a time.
 32. Apparatus as claimed in claim 31 comprising a relay in series with the electrical supply to one of the heaters and arranged such that the contacts thereof are opened when power is supplied to the other heater.
 33. Apparatus as claimed in claim 31 wherein the arrangement is such as to cut off power to the removable liquid heating vessel when the heater of the second heating chamber is energized. 